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CABLES + CABLE ACCESSORIES
Beyond this, however, there are also applications which are so
specific that an individual solution needs to be developed. This was
the case when a major German manufacturer of buses made their
request. The reason behind this is the standard ECE-R 118.01 and the
announcement of the Economic Commission for Europe (ECE) three
years ago that the fire protection requirements for cables installed in
buses would be made stringent at the end of 2015. The new standard
concerns cables which are installed in the passenger compartment,
but not cables in the engine compartment, which already have their
own equally stringent standards. The new standardmade it necessary
to develop new cables.
The regulation aims to protect passengers in the event of a fire.
Sixty percent of all victims in fire incidents are not killed by the fire
itself but by inhaling toxic gases, particularly carbon monoxide. It
becomes a precarious situation when cables are present at the scene
of the fire. Cables which have to meet special fire protection require-
ments are often made from Polyvinylchloride (PVC) and contain
halogens – chemical elements in the seventh group of the periodic
table including fluorine, chlorine and bromine – as flame retardants.
These additives prevent the cable sheath from getting burnt away
and make it easier to extinguish the fire on the cable once the exterior
cause of the fire has stopped, for instance when the fire-fighters have
extinguished it. PVC cables are therefore the number one choice in
the engine compartment of cars.
Although PVC cables burn slowly in a fire, they produce a high
volume of smoke. Furthermore, they outgas halogens, including
large volumes of chlorine. If chlorine gas comes into contact with
water – when the fire is extinguished, or if smoke enters airways –
hydrogen chloride (hydrochloric acid) is formed and also acids such
as hydrogen fluoride (hydrofluoric acid) and hydrogen bromide, as
well as toxic dioxins. The acids chemically burn airways and in the
worst case scenario can result in death. Therefore PVC cables with
halogens are not necessarily a bad choice in areas with a high risk of
fire – but only if there are no people nearby. This is the reason why
PVC flooring is no longer used in public buildings.
PVC cables are taboo in passenger compartments
Such cables have no place in the passenger compartments of buses,
where many cables are more or less installed openly, for example
those for ticket machines, destination displays and surveillance cam-
Abbreviations/Acronyms
The use of Ethernet cables
is constantly increasing.
ECE
– Economic Commission for Europe
PC
– Personal Computer
PUR
– Polyurethane
PVC
– Polyvinylchloride
eras – and this finding forms the basis of ECE-R 118.01. So when the
request came from the bus manufacturer, cables with PVC sheaths
were out of the question. In industry, the alternative to PVC is Polyu-
rethane (PUR). The material has some outstanding properties – it
is extremely resistant to oil and many chemicals and is also highly
resistant to abrasion and movements which are repeated millions of
times, for instance in machinery. PUR also has a few disadvantages
though: it is prone to hydrolysis, meaning that it absorbs water, which
however is not of any consequence when used in the interior of a bus.
The second disadvantage, however, is all the more serious: PUR has
worse fire properties than PVC.
The challenge for the Lapp engineers was thus to bring the fire
behaviour of PUR up to the same level as that of PVC. The developers
managed this with a PUR formulation containing various additives.
These substances do not represent any health risk even if they escape
into the air during a fire. The additives do not contain any halogens,
which is also the case for PUR cables in general. After three years
of development work, with the process of acquiring the certification
at one of Germany's two assigned testing laboratories itself taking
a whole year, the Lapp developers were able to announce their suc-
cess. The new cable meets the requirements of the new standard
ECE-R 118.01, specifically regarding the fact that it does not contain
halogens or any other toxic substances.
Cable with fire retardant
The cable meets the requirements of the compulsory flame test: a
flame is held towards the lower end (10 cm along) of a length of cable
measuring 60 cm in total, and is then taken away after 15 seconds.
The fire on the cable sheath must go out on its own within 70 sec-
onds, and once it has extinguished by itself, at least five centimetres
at the upper end of the cable must remain undamaged. A PUR cable
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October ‘15
Electricity+Control